Electric outlet having means to lock the prongs of an attachment plug therein



March 22, 1955 R.. SMITH ELECTRIC OUTLET HAVING MEANS TO LOCK THE PRONGSOF AN ATTACHMENT PLUG Tl-IEREIN Filed lay 24, 1954 2 Sheets-Sheet l fWffgg E M /3 1 2/ 23 /6 7 .19 3 gm 6 J v 3/ Z6 iFZLZZ I I I 6 INVENTOR.

Wilbur 7?. 3/77/27? .March22, 1955 w. R. SMITH 2,704,831

ELECTRIC OUTLET'HAVING MEANS TO LOCK THE PRQNGS N OF AN ATTACHMENT PLUGTHEREI 2 Sheets-Sheet 2 Filed May 24, 1954 Wilbur 2291 559933 7;

United States Patent ELECTRIC OUTLET HAVING MEANS TO LOCK THE PRONGS OFAN A'ITACHlVlENT PLUG THEREIN Wilbur R. Smith, Clarkston, Wash.

Application May 24, 1954, Serial No. 431,827

4 Claims. (Cl. 339-91) This invention relates to an electrical outlet.

One object of the invention is to provide an outlet of such constructionthat a person will not be liable to receive an electric shock bycareless handling of a plug.

Another object of the invention is to provide an electric outlet with acylinder adapted to receive a terminal plug, the cylinder beingrotatable about its axis from a normal position wherein the circuit isbroken, to a position wherein the circuit is made to the plug and dangerof accidental shorting of the circuit eliminated.

Another object of the invention is to provide an electric outlet havinga rotatable cylinder of such construction that when the terminal plug isinserted and the cylinder rotated, plungers are moved into lockingengagement with the plug prongs and danger of accidental removal of theplug from the outlet is eliminated.

Another object of the invention lies in the provision of an electricoutlet including a rotatable cylinder having contact bars adapted toelectrically connect with contact strips carried by the outlet body whenthe cylinder is I0- tated, by means of a plug having its prongs disposedwithing the sockets formed in the cylinder, so that electricalconnecting and disconnecting is accomplished between the contact barsand contact strips instead of between the plugs of the prong and thesockets as in conventional outlets.

Another object of the invention lies in the provision of an electricaloutlet having a rotatable cylinder adapted to receive the prongs of aterminal plug and having means for locking the prongs in the cylinderduring the period that contact is made between the contact bars of thecylinder and contact strips of the outlet and releasing the prongs onlyafter contact is broken between said bars and strips.

These and other objects of the invention will become apparent during thecourse of the following description.

In conventional electric outlets where the prongs of the terminal plugare admitted to the contact bars within the outlet which are permanentlyconnected to the electric wiring system, it is possible to receive anelectric shock by touching the prongs during the insertion or removal ofthe terminal plug with relation to the outlet. Also, when heavy loadsare being carried by the circuit, the making and breaking of theelectrical connection between the prongs and the contact bars causesarcing and burning of the elements and in addition the terminal plug isheld into the outlet by frictional engagement only and often isaccidentally removed therefrom. The present invention seeks to overcomeall of these undesirable conditions.

In the accompanying drawing, forming a part of this specification, andin which like numerals are employed to designate like parts,

Figure 1 is a face view of a wall outlet having a cover plate secured inplace;

Figure 2 is a vertical cross section taken through the outlet andincluding a terminal plug in one cylinder;

Figure 3 is a rear elevation of the improved outlet with the rear coverremoved;

Figure 4 is a transverse cross section taken through the outlet midwayits length;

Figure 5 is a fragmentary longitudinal cross section on a plane 90degrees from that of Figure 2 and showing one cylinder; and

Figure 6 is a perspective view of the rear and one side of the outletwith the rear cover removed.

Referring now more particularly to the drawing, the improved outlet hasbeen shown as a double electric outlet and has a body 10 formed frominsulating material. This body, like conventional outlets, is adapted tobe secured within an outlet box (not shown) and has a face plate 11releasably secured thereto to conceal the box. In the body are formedlongitudinally spaced annular cavities 12 open at their front and rearends and having reduced front end portions 13 defined from the enlargedrear end portions 14 by an intermediate annular shoulder 15. Disposedwithin each cavity is a cylinder 16 which has an enlarged rear endportion 17 and a reduced front end portion 18 and having an intermediateshoulder 19 which bears against the shoulder 15 and prevents removal ofthe cylinder forwardly out of the cavity 12 and yet permits axialrotation of the cylinder therein. The cylinders are of dimensions tohave close tolerance within their respective cavity 12.

Inspection of Figures 2, 3, and 5 will reveal that the enlarged portions14 of the cavities 12 are provided with diametrically opposed crescentshaped recesses constituting cam surfaces 20, thus causing the enlargedportion 14 to appear eliptical or oblong in cross section.

Each cylinder 16 is provided with a pair of sockets 21 spaced anddisposed to receive the prongs 22 of conventional terminal plugs as 23.It will here be noted that the conventional prongs 22 of plugs 23 areprovided with axially aligned apertures at 24 and these are employed inthe exercise of this invention and the manner of use will be moreparticularly disclosed hereinafter.

Each socket 22 is provided with a contact bar 25 which is formed from astrip of conductive material folded upon itself midway its length andthe resulting bar has the folded end bent at substantially a right angleto form a lip 26. The contact bars 25 are inserted into the sockets 21from the rear end of the cylinder 16 with the spaced open ends towardthe front of the cylinder 16 and the right angle lips 26 extendingradially at the rear end of the cylinder 16 and disposed diametricallyopposed to each other.

Substantially midway the length of the cylinder 16 I provide radialbores 27 which communicate from the peripheral face of the annularcylinder 16 one with each socket 21. It will also be noted that one leafof the bars 25 is drilled or otherwise provided with an aperture 28 toadmit a plunger 29 into the socket 21. The plunger is disclosed ashaving a substantially hemispherical end face 30 and it will be seenthat the rear end of the plunger extends into the crescent shapedrecesses or cam areas 20 so that the faces 30 are retracted from thesockets 21 a sufiicient distance to permit admission of the prongs 22 ofthe terminal plug 23. However, when the cylinder 16 is rotatedsubstantially degrees the cam surfaces 20 cause the plungers 29 to shiftinwardly into the sockets 21 and lock the prongs 22 therein. Obviously,the plungers 29 may enter into the apertures 24 as disclosed in Figure 5to lock the prongs or the hemispherical end face 30 may enter a smalleraperture only insofar as it is physically capable and still lock theprong in the sockets. If no aperture 24 is provided the plungers thenare forced against the side faces of the prongs 22 to lock them thereinby clamping action. This use is disclosed since it is conceivable thatprongs having no aperture 24 may be manufactured and their use would notbe obviated by the change in the structure.

On its rear face the body 10 is provided with a pair of opposed contactstrips 31 and these strips are carried by the body and tangentiallyarranged at the rear end of the cavities 12 in such position that whenthe cylinders 16 are rotated 90 degrees from their normal position,wherein the lips 26 are disposed in longitudinal alignment with thelongitudinal dimension of the body 10, to a contacting position, whereinthe lips 26 are disposed laterally of the body 10, they are frictionallyengaged with the contact strips 31 for electrical connection thereto. Itwill thus be seen that when the contact bars 25 are electricallyconnected to the contact strips 31 the plungers 29 are forced inwardlyand the prongs 22 of the terminal plug 23 are locked within the sockets21 of the cylinder 16 against accidental removal, therefore,

making and breaking of the electrical connection is accomplished betweenthe contact strips 31 and the lips 26 and these may be made ofsufiiciently heavy material to prevent burning or damage by this action.The contact strips are provided with bifurcations 31a which are definedby upper and lower bars 31b and 310 and the lips 26 pass intermediatethese bars and into the bifurcations where electrical contact is made.The electrical contact strips 31 are secured to the body by means ofscrews 32 and by this means also the cylinders 16 are secured againstremoval from the body rearwardly since the contact strips cover aportion of the cavities 12.

It will be seen in Figure 4 that the bolts 32 thread into a metalconnector 33 carried by the body and this connector is provided withcircuit connecting bolts 34 to which the conventional house wiring issecured.

A rear cover plate 35 is secured by bolt 36 to an internally threadedboss 37 carried by the body 10 and is removable for access to the rearof the outlet.

The body is provided with longitudinally extending wedge shaped stops 38which bind the lips 26 when the cylinders are rotated to their normalposition and prevent rotation beyond a position wherein the lips 26 aredisposed longitudinally of the body 10. To prevent movement beyond thecontact position shown in Figure 6 the rear end face of the cylinders 16are provided with bosses 39 which are adapted to strike the stops 38 andlimit the rotational movement of the cylinder 16 to substantially 90degrees from the normal position.

Having thus described my invention, I claim:

1. An electric outlet comprising a body of insulation formed with acavity open at its front end; a pair of opposed spaced contact stripscarried by the body and diametrically arranged at the rear end of saidcavity; a revolvable cylinder in said cavity and having a pair ofcontact bars disposed in spaced sockets for receiving and electricallycontacting the prongs of a conventional electric plug; said contact barshaving lips at the rear end of said cylinder for electrically connectingto said contact strips when said cylinder is rotated from its normalposition; a plunger carried by the cylinder and radially movable thereininto and out of locking relation with respect to a plug prong disposedfor the time being in one said socket; and means operable when saidcylinder is rotated to move said plunger inwardly to the lockingposition when the cylinder is rotated from its normal position.

2. An electric outlet comprising a body of insulation formed with acavity open at its front and rear ends; a pair of opposed spaced contactstrips carried by the body at opposite sides of the cavity anddiametrically arranged at the rear end thereof; a revolvable cylinder insaid cavity and having a pair of contact bars disposed in spaced socketsfor receiving and electrically contacting the prongs of a conventionalelectric plug; said contact bars having radially extending diametricallyopposed lips at the rear end of said cylinder and adapted toelectrically connect to said contact strips when said cylinder isrotated substantially 90 degrees from its normal position; a plungerslidably carried by said cylinder and movable diametrically thereof intoone said socket and through an aperture in one said contact bar into andout of locking relation with respect to a plug prong disposed withinsaid socket; said cavity having an eliptical cross sectionalconfiguration constituting a cam surface; and said plunger engaging saidcam surface and thereby moved inwardly to the locking position when thecylinder is rotated substantially 90 degrees from its normal position.

3. An electric outlet comprising a body of insulation formed with acavity open at its front and rear ends; said cavity being annular andhaving a reduced forward end portion and an enlarged rear end portiondefined by an intermediate annular shoulder; a pair of opposed spacedcontact strips carried by the body at opposite sides of the cavity andtangentially arranged at the rear end thereof; a revolvable cylinder insaid cavity and having a pair of contact bars disposed in spaced socketsfor receiving and electrically contacting the prongs of a conventionalelectric plug; said cylinder having a reduced forward end portion and anenlarged rear end portion defined by an intermediate shoulder andadapted to fit into said cavity with close tolerance for rotationtherein; said contact bars having means for electrically connecting tosaid contact strips when said cylinder is rotated substantially 90degrees from its normal position; a plunger slidably carried by saidcylinder and movable diametrically thereof into one said socket throughan aperture in one said contact bar into and out of locking relationwith respect to a plug prong disposed within said socket; said cavityhaving a cam face cooperating with said plunger for moving said plungerinwardly to the locking position as the cylinder is rotatedsubstantially degrees from its normal position.

4. In an electric outlet having a rotatable cylinder normallydisconnected from an electrical circuit and adapted to receive andelectrically contact the prongs of a conventional electric plug; meansfor securing said prongs in said cylinder comprising a plunger carriedby the cylinder and movable radially therein into and out of lockingrelation with respect to a plug prong disposed for the time beingtherein; and means including a cam surface engageable with said plungeroperable when said cylinder isrotated to move said plunger inwardly tothe locking position as the cylinder is rotated substantially 90 degreesfrom its normal position.

References Cited in the file of this patent UNITED STATES PATENTS1,657,004 Douglas Jan. 24, 1928 1,669,666 Laub May 15, 1928 1,774,230Fagerlund Aug. 26, 1930 2,040,113 Von Holtz May 12, 1936 2,175,472Kuhlman Oct. 10, 1939 2,215,316 Benander Sept. 17, 1940

